A thermoplastic resin, for example a polyester-series resin, has excellent mechanical and electrical properties, weather resistance, water resistance, and resistance to chemicals and solvents. Therefore, the resin is used as an engineering plastic in various purposes such as electric or electronic device parts, mechanical device parts and automotive parts. While, the polyester-series resin is required to have improved mechanical properties and to be flame-retardant from viewpoint of safety as the field of their uses expands. As a flame retardant for generally imparting high flame-retardancy to a resin, a halogen compound or an organic phosphorus-containing compound has been known. However, a halogen-containing flame retardant is not preferable for environmental reasons because the flame retardant sometimes generates a large amount of a dioxin-series compound on resolution caused by combustion. In addition, an organic phosphorus-containing flame retardant is a causative factor of a sick house syndrome which has been a problem recently, and is not preferred from the viewpoint of safety.
On the other hand, there has been proposed a flame-retardant resin composition to which flame retardancy is imparted by using a flame retardant which is not an organic phosphorus-containing nor halogen atom-containing one. For example, Japanese Patent Application Laid-Open No. 255811/1997 (JP-9-255811A) (Patent Document 1) discloses a flame-retardant resin composition which comprises a thermoplastic resin such as a polystyrene resin, a polypropylene resin or a polyamide resin, and a reaction product of melamine and sulfuric acid as a flame retardant. Moreover, Japanese Patent Application Laid-Open No. 511409/1998 (JP-10-511409A) (Patent Document 2) discloses that a melamine condensate which is obtained from condensation of melamine or a melamine salt by using an organic acid such as sulfonic acid imparts flame retardancy to a polyamide resin, an ABS resin, and a polyurethane resin. Further, Japanese Patent Application Laid-Open No. 288361/2001 (JP-2001-288361A) (Patent Document 3) discloses a flame-retardant polyamide resin composition containing melam methanesulfonate as a flame retardant.
These flame retardants, however, cannot certainly impart enough flame retardancy to a broad variety of resins (in particular, a polyester-series resin).
Patent Document 1: JP-9-255811A
Patent Document 2: JP-10-511409A
Patent Document 3: JP-2001-288361A